"That put us in a scramble for the next 2 1/2 years," said Richard Cook, Theisinger's deputy who succeeded him last February.

Cook, like Theisinger, has a great sense of humor – an indispensable attribute for someone involved in such a high-visibility, sometimes unpredictable job.

"JPL and NASA have developed a structured way of doing business over the years," he said. "When you have a schedule crunch like we had, it puts a lot of pressure on that approach and it's almost impossible to do. The team had to invent new ways of doing business and remain very nimble to get the job done."

Rover wheels unfolding

The wheels of NASA's Mars Exploration Rovers were specially designed to fold up tightly inside the spacecraft and unfold after landing. Read a feature article about the design work on the wheels. View a video about some of the challenges of getting to Mars.Image/video credit: NASA/JPL

The first big problem was mass. The team had to downsize the rover to fit the spacecraft and the lander. For example, they redesigned the wheels to be hollow on the inside so they were lightweight, compact, and yet rugged enough to handle the hostile martian terrain.

Usually, when engineers redesign a spacecraft, they leave at least 30 percent of wiggle room to accommodate the unexpected. This time, they had only 10 percent. Imitating the reality television show Survivor, the team started holding "mass tribal councils" to keep the mass in check. "I fully intended to throw people off the spacecraft, but never got the chance," joked Cook. Of course, there weren't any people on the spacecraft, just parts. "We made sure that everyone on the team worked to reduce the mass of each and every component."

Petals close around rover

As workers watch, the petals of the lander close around one of NASA's Mars Exploration Rovers at Kennedy Space Center in Florida prior to launch. Image credit: NASA/JPL

In August 2002, less than a year before launch, the team began putting all the spacecraft parts together. They worked two shifts continuously getting the spacecraft ready for transport to Cape Canaveral, Florida. Even after delivering the spacecraft, they continued testing its systems. On one occasion, they had problems with the cable cutters that set the rovers free. On another occasion, they had problems with the electronics that operated the rover. Like child engineering prodigies taking apart and reassembling radios and computers, they took the spacecraft apart twice and put it back together.

Jim Erickson

Jim Erickson has succeeded Pete Theisinger and Richard Cook as the project manager for NASA's Mars Exploration Rovers at JPL, as both rovers continue to explore the surface of Mars long after completing their primary missions. Image credit: NASA/JPL